Hematopoietic stem cells (HSCs) are a subset of multipotent stem cells that are responsible for the ability to sustain lifelong hematopoiesis, and continuously generate myriad and various blood cell types, while maintaining adequate number of stem cells in the bone marrow. Hematopoietic stem cells give rise to all the blood or immune cell types, including monocytes and macrophages, neutrophils, basophils, eosinophils, erythrocytes, megakaryocytes/platelets, dendritic cells, T-cells, B-cells, NKT-cells, and NK-cells. Hematopoietic tissues contain cells with long-term and short-term regeneration capacities, and committed multipotent, oligopotent, and unipotent progenitors.